Greenhouse gas related climate feedbacks from arctic ecosystems

Transcription

1 Greenhouse gas related climate feedbacks from arctic ecosystems Torben R. Christensen Department of Physical Geography and Ecosystem Science, Lund University, Sweden & Arctic Research Centre, Aarhus University, Denmark ARKTIKO seminar, Helsinki 10 May 2016

2 Outline Introduction where do we come from in the Nordic countries Practical work in the field with arctic GHG exchanges Examples of sensitivities UN and Arctic Council initiated synthesis assessments

3 Outline Introduction where do we come from in the Nordic countries Practical work in the field with arctic GHG exchanges Examples of sensitivities UN and Arctic Council initiated synthesis assessments

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6 Study sites Mobile tower 6

7 Summarising Arctic carbon fluxes 7 Parmentier et al. Nature Climate Change 2013

8 Complexities: Translocation and attenuation of the permafrost carbon feedback Vonk and Gustafsson (2013) Nature Geoscience

9 Outline Introduction where do we come from in the Nordic countries Practical work in the field with arctic GHG exchanges Examples of sensitivities UN and Arctic Council initiated synthesis assessments

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11 Experiments in nature: Creating experimental conditions for the study of CO 2 fluxes in new sea ice Photo: Søren Rysgaard

12 CO 2 fluxes over sea-ice in Young sound in March 2012

13 A bear selfie Zackenberg, NE Greenland, 29 April 2016

14 Adventdalen film

15 Outline Introduction where do we come from in the Nordic countries Practical work in the field with arctic GHG exchanges Examples of sensitivities UN and Arctic Council initiated synthesis assessments

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17 Sea Ice Connections to Methane Parmentier et al., Nature Climate Change, 2013

18 Experimental setup Experiment - summer 2010 High arctic habitat in northeast Greenland Zackenberg (74 30 N 20 30W) Muskox Ovibos moschatus Mire/grassland - main grazing area during summer and autumn Five blocks; each with one control and two treatments: Exclosure and Snowcontrol Measurements in the growing season of 2011, 2012 and 2013 CO2 & CH4 fluxes - closed chamber technique portable FTIR (Fourier Transform Infrared) spectrometer (Gasmet Dx 40-30, Gasmet Technologies Oy) Ecosystem variables: soil temperature, active layer depth, water table depth Vegetation analysis in 2011 and 2013 Harvested biomass samples in August 2013 Photo: Lars Holst Hansen

19 Three years after initiation of the exclosures vegetation structure had changed Dry biomass (g) Control Exclosure Snow-control Litter 70 % * * * * Mosses 35 % * Carex Dup Erioph Moss Litter Total bio Fig: g ± SE of samples harvested (20*20 cm) in Sign. differences, * p 0.05 The height of Dupontia fisheri ssp. Psilosantha, Eriophorum scheuchzeri and mean height of all vascular leaves were significantly higher in ungrazed areas (approximately 27 %) Falk et al., ERL July 2013

20 CH4 flux (mg CH4 m-2h-1) Three years after initiation of the exclosures CH4 fluxes had changed Control CH4 44 % *** 2011 Year Arctagrostis C EX Exclosure Dupontia C EX 2012 Eriophorum C EX Fig: Mean CH4 flux ± SE in wet blocks *** p Equisetum C EX Sum C EX 2011 Mean Max Min p 340 ± ± ± ± ± ± ± ± ± ± Mean Max Min p 185 ± ± ± ± ± ± ± ± ± ± Falk et al., ERL 2015 Table: No of vascular plants tillers per m-2 ±SE, Sign. differences bold.

21 Sensitivity of the permafrost ecosystems

22 Snow depth Johansson et al. 2013

23 Active layer thickness Updated from Johansson et al. 2013

24 0.8 Total average for CH 4 emissions in control and manipulated plots mg CH 4 m -2 h Control Manipulated Dahlbom, Mastepanov & Christensen in prep.

25 Outline Introduction where do we come from in the Nordic countries Practical work in the field with arctic GHG exchanges Examples of sensitivities UN and Arctic Council initiated synthesis assessments

26 Fate of Anthropogenic CO 2 Emissions ( average) 8.6 ± 0.4 GtC/yr 92% 4.3±0.1 GtC/yr 45% 0.8 ± 0.5 GtC/yr 8% ± 0.5 GtC/yr 27% 2.6 ± 0.8 GtC/yr 27% Calculated as the residual of all other flux components Source: Le Quéré et al 2013; CDIAC Data; Global Carbon Project 2013

27 ATMOSPHERIC PERSPECTIVE CO 2 : 0.4 ± 0.4 Pg C yr -1 surface sink CH 4 : Tg CH 4 yr -1 surface source ADJACENT OCEAN EXCHANGE DIC: ~1.1 Pg C yr -1 DOC: Tg C yr -1 CH 4 : Gg CH 4 yr -1 SEA ICE ARCTIC OCEAN STOCKS DIC: 310 Pg C DOC: 9 Pg C SEDIMENT: 9 Pg C CH 4 : 0-3 Tg CH 4 CO 2 : Tg C yr -1 sink Flux to Sediment: ~2 Tg C yr -1 CH 4 : 1-12 Tg CH 4 yr -1 source River POC: ~6 Tg C yr -1 River PIC: 0 4 Tg C yr -1 Erosion POC: ~8 Tg C yr -1 Flux to Sediment: ~9 Tg C yr -1 DIC: ~43 Tg C yr -1 DOC: ~33 Tg C yr -1 CH 4 : 1-11 Gg CH 4 yr -1 SUBMARINE PERMAFROST CH 4 HYDRATE: 2-65 Pg CH 4 CO 2 : Tg C yr -1 source CO 2 : Pg C yr -1 sink CH 4 : Tg CH 4 yr -1 source ARCTIC LAND STOCKS VEG: Pg C SOIL: Pg C SUBTERRANEAN INTRA- and SUB-PERMAFROST CH 4 HYDRATE: Pg CH 4 ARCTIC OCEAN FLOOR CH 4 HYDRATE: Pg CH 4 McGuire et al. Ecological monographs, 2009

28 For AMAP technical report on methane - projections A medium (25 Tg CH 4 /yr) A large (50 Tg CH 4 /yr) An extreme (100 Tg CH 4 /yr) - scenario for natural emission change by 2050 was used. This assessed in relation to global-mean concentrations until 2050 assuming different scenarios for anthropogenic emissions. Future concentrations are calculated by a Box model, using the CLE (left panel) or MFR-AC8 (right panel) scenarios for anthropogenic emissions, and the different (linear) increases above in natural emissions, in addition to the baseline natural emissions of 202 Tg(CH 4 )/yr. 28

29 Natural emission change impact Extra global warming < 0.1 ⁰C Gauss, Avorek, and the AMAP CH 4 expert team, 2015.

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31 Hope and Schaefer, 2015

32 Basic message Natural Arctic GHG changes are still small in importance for climate over the coming years compared with the effect of global anthropogenic emissions We have no evidence to say we are looking towards an apocalypse based on natural emission changes.. Anthropogenic emissions rule the changing climate and these emissions are unfortunately far more powerful than any of the natural ecosystem processes. But this does not mean we do not have some important unknowns and interesting basic science issues to address in the natural arctic environments 32

33 Thank you for your attention